Math & Numbers

Roman Numeral Converter

Convert between numbers and Roman numerals.

Enter a number (1-3999) to convert it to Roman numerals, or enter a Roman numeral to convert it back to a number.

Enter a number between 1 and 3999.

Roman Numeral

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Enter a valid Roman numeral.

Number

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How to Use This Tool

  1. To convert a number to Roman numerals, enter a number between 1 and 3999 and click Convert.
  2. To convert a Roman numeral back to a number, enter it in the second field and click Convert to Number.

How Roman Numerals Work

Roman numerals use seven basic symbols: I (1), V (5), X (10), L (50), C (100), D (500), M (1000). Numbers are formed by combining these symbols, generally from largest to smallest, and adding their values.

The Subtractive Notation Rule

When a smaller-value symbol appears before a larger one, it's subtracted rather than added — for example, IV = 4 (5-1), IX = 9 (10-1), XL = 40 (50-10), and CM = 900 (1000-100). This subtractive notation avoids repeating a symbol more than three times in a row.

Why the Range Is Limited to 3999

Standard Roman numerals don't have a widely agreed-upon symbol for numbers 4000 and above without additional notation (like a bar over a numeral to indicate multiplication by 1000), so this converter is limited to the standard 1-3999 range.

Common Uses Today

Roman numerals remain in use for clock faces, book chapter/volume numbering, Super Bowl and Olympic Games numbering, movie sequel numbering, and formal document sections.

Frequently Asked Questions

Why can't I convert numbers above 3999?

Standard Roman numeral notation doesn't have a universally agreed-upon way to represent 4000 and above using the basic symbols alone — larger numbers historically required additional notation like an overline to indicate multiplication by 1000.

What does the subtractive rule mean, like in "IV" for 4?

When a smaller numeral appears directly before a larger one, it's subtracted rather than added — so IV means 5 minus 1 (4), avoiding writing "IIII" (four I's in a row), which Roman numeral convention avoids.

This calculator is provided for general informational and estimation purposes only. Results should not be treated as professional financial, tax, legal, medical, or engineering advice. Always verify critical calculations with a qualified professional or official source before making decisions.